Abstract Primary mucinous carcinoma of the skin (PMCS) is a rare malignant adnexal tumor arising from sweat glands, most commonly affecting elderly males. Clinically, it often mimics benign lesions and other cutaneous malignancies, leading to frequent misdiagnosis. This report highlights the case of a 74-year-old male who presented with a one-year history of a painless swelling over the left cheek. Examination revealed a 3 cm × 3 cm nontender, reddish growth over the left zygomatic region without lymphadenopathy. The lesion was excised with wide local margins. Histopathological evaluation demonstrated dermal-based mucin pools containing islands of mildly pleomorphic epithelial cells, consistent with mucinous carcinoma, with positive resection margins. Systemic imaging and endoscopic evaluation excluded an internal primary malignancy, confirming the diagnosis of PMCS. Periodic acid–Schiff staining was positive, and immunohistochemistry supported an adnexal origin. PMCS is an indolent but locally recurrent tumor, and differentiation from metastatic mucinous carcinoma is essential through appropriate imaging and histopathologic studies. Although the debate persists regarding its eccrine versus apocrine origin, the lesion’s behavior supports a sweat gland lineage. Wide local excision remains the treatment of choice, as chemotherapy and radiotherapy have limited roles. Due to the risk of recurrence, long-term follow-up is recommended, with tumor markers such as CEA and CA15.3 potentially useful for surveillance.
Thakur et al. (Wed,) studied this question.